linux-kernel - Re: [PATCH v6 0/4] mmc: sdhci-of-arasan: Enable UHS-1 support for Keem Bay SOC

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Date:   Wed, 2 Dec 2020 15:10:04 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Michal Simek <michal.simek@...inx.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Raja Subramanian, Lakshmi Bai" 
        <lakshmi.bai.raja.subramanian@...el.com>,
        Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@...el.com>,
        Mark Gross <mgross@...ux.intel.com>
Subject: Re: [PATCH v6 0/4] mmc: sdhci-of-arasan: Enable UHS-1 support for
 Keem Bay SOC

On Wed, 2 Dec 2020 at 14:09, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>
> On Wed, Dec 2, 2020 at 2:44 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > On Wed, 2 Dec 2020 at 13:24, Shevchenko, Andriy
> > <andriy.shevchenko@...el.com> wrote:
> > > On Wed, Dec 02, 2020 at 11:53:42AM +0100, Ulf Hansson wrote:
> > > > On Wed, 2 Dec 2020 at 08:02, <muhammad.husaini.zulkifli@...el.com> wrote:
> > >
> > > ...
> > >
> > > > > Kindly help to review this patch set.
> > > >
> > > > This version looks a lot better to me, but I am still requesting you
> > > > to model the pinctrl correctly. I don't see a reason not to, but I may
> > > > have overlooked some things.
> > >
> > > I'm wondering why we need to mock up a pin control from something which has no
> > > pin control interface. It's rather communication with firmware that does pin
> > > control under the hood, but it also may be different hardware in the other /
> > > future generations. Would you accept mocking up the same calls over the kernel
> > > as pin control, as something else?
> >
> > Well, my point is that modeling this a pinctrl would keep the mmc
> > driver portable. Additionally, it's very common to manage pinctrls in
> > mmc drivers, so it's not like this is an entirely new thing that I
> > propose.
> >
> > If/when it turns out that there is a new HW having a different pinctrl
> > interface, it would just mean that we need a new pinctrl driver, but
> > can leave the mmc driver as is.
>
> My point is that it may be *not* a pin control at all.

Sorry, but I don't quite follow, what is *not* a pinctrl?

According to the information I have received from the previous
discussions [1], it's clear to me that the ARM SMC call ends up
changing settings for the I/O-pads. Or did I get that wrong?

> And in that case you will need to mock up (what exactly?) and update
> the MMC driver.
>
> --
> With Best Regards,
> Andy Shevchenko

Kind regards
Uffe

[1]
https://lkml.org/lkml/2020/10/8/320